Compaction Method and Device for Automated Fiber Placement

ABSTRACT

A compaction device for use with an automated fiber placement machine includes multiple compaction rollers mounted for independent displacement on a supporting frame. The attitude of the compaction rollers change relative to each other when fiber tows are laid up at an angle over an edge of a tool in order to maintain compaction pressure on the tows and thereby reduce non-compacted areas of the tows.

BACKGROUND INFORMATION

1. Field

The present disclosure generally relates to methods and equipment forlaying up composite parts using automated fiber placement, and dealsmore particularly with a method and device for compacting fiber tows,particularly fiber tows having angular fiber orientations.

2. Background

Automated fiber placement (AFP) machines are used in various industriesto layup composite parts, particularly small parts and/or those havingcomplex geometries, to increase rate and precision. AFP machines place abandwidth of fiber tows on a layup tool such as a mold tool or layupmandrel. The fiber tows may be in the form of split tape, and maycomprise thermoset or thermoplastic pre-impregnated unidirectional fiberreinforcements that are laid up in various fiber orientations e.g., 0°,+/−45°, +/−60°, 90°. A bandwidth of the tows are dispensed, cut tolength and compacted onto the tool by an AFP head that is typicallyautomatically controlled by a numerically controlled robot or similarmanipulator. The incoming fiber tows are often heated to increase theirtack before being fed beneath a single compaction roller that bothapplies and consolidates and/or debulks the entire bandwidth of towsonto the layup tool as the AFP head moves over the tool surface.

Difficulties may be encountered when laying up fiber tows along a pathforming an angle relative to an edge on the tool. For example, whenlaying up fiber tows with +45 or −45° orientations over two toolsurfaces intersecting to form a right angle edge, such as a horizontalsurface and the vertical surface, there is a resultant area ofnon-compaction as the roller transitions over the right angle edge andmust lift off of the horizontal surface in order to rotate the fullbandwidth of tows onto the vertical surface. In the past, this problemhas been addressed by making additional passes with the AFP machine overthe non-compacted areas, however this approach increases the layup timeand associated costs. Another problem associated with using a singlecompaction roller is the need for laying up additional tow material onthe vertical surface in those part applications where an edge of thepart falls below a minimum layup distance beyond the area ofnon-compaction.

Accordingly, there is a need for a method and compaction device for usewith AFP machines that reduces the non-compaction area caused by thecompaction roller lifting off of the tool surface as it transitions overhigh angle features. There is also a need for a method and compactiondevice of the type mentioned above which reduces the need for laying upadditional tow material where the edge of the part falls under a minimumlayup distance beyond an area of non-compaction.

SUMMARY

The disclosed embodiments provide a method and device for compactingfiber tows on a substrate such as a tool, using automated fiberplacement. The device comprises a plurality of compaction rollersmounted for independent movement on a frame forming part of an automatedfiber placement head. The use of multiple compaction rollers of smallerdiameter, compared to a single larger compaction roller, maintainscompaction pressure on the fiber tows at the radius of edge transitionson a layup tool, and in some embodiments may reduce the non-compactedareas of the layup tool to only half of the width of a single one of thetows. The compaction rollers are spring biased to force and compact thefiber tows onto the tool, but may change in attitude (spatialorientation) relative to each other when traversing over an edge betweentwo non-planar tool surfaces in order to maintain contact with the tooland thereby reduce non-compacted areas on the layup. The use of multiplerollers combined with staggered cut/add of the tows at the end of thecourses result in a crenulated, near net trim that reduces materialwaste. The embodiments may reduce layup time and improve part quality byreducing voids caused by non-compaction of fiber tows, and materialcosts may also be reduced through reduction of scrap.

According to one disclosed embodiment, a device is provided forcompacting a bandwidth of fiber tows on a tool. The device comprises aframe adapted to be moved over surfaces of the tool, and a plurality ofcompaction rollers mounted on the frame for independent relativedisplacement. Each of the compaction rollers adapted to compact the towsonto the surfaces of the tool. The frame may include a pair of spacedapart arms, and the compaction rollers extend between and have oppositeends thereof respectively rotatably mounted on the pair of arms. Each ofthe compaction rollers has first and second opposite ends. Pins fixed toeach of the first and second ends of the compaction rollers slidelymount the compaction roller on the frame. The device may also comprisesprings on the pins for biasing the compaction rollers toward thesurfaces of the tool. The compaction rollers extend substantiallyparallel to each other. The tows each have a width, and there is a pitchbetween centers of the compaction rollers. The pitch is substantiallyequal to the width of the tows. The compaction rollers normally lie in asingle plane, and at least certain of the compaction rollers are adaptedto move out of the single plane when the compaction rollers traverseover an edge between surfaces of the tool. The device may furthercomprise a bearing block at each end of each of the compaction rollers,wherein each end of the compaction rollers is journaled for rotation inone of the bearing blocks. The pins are respectively fixed to thebearing blocks and are slidable on the frame. The springs arerespectively sleeved over the pins for biasing the bearing blocks towardthe tool surfaces. The compaction rollers are equal in number to thefiber tows.

According to another disclosed embodiment, a device is provided forcompacting a bandwidth of fiber tows on a tool having tool surfacesintersecting at an angle forming an edge on the tool. The devicecomprises a pair of arms spaced apart from each other, and a pluralityof displaceable compaction rollers extending between the arms andmounted on the arms for independent displacement relative to each otheras the compaction rollers traverses over the edge on the tool. Each ofthe compaction rollers is spring biased toward the tool surfaces. Thecompaction rollers extend substantially parallel to each other andnormally lie in a single plane, but are individually displaceable out ofthe single plane when traversing over the edge on the tool. Thecompaction rollers are substantially equal in number to the fiber towsin the bandwidth. The distance between centers of adjacent ones of thecompaction rollers is substantially equal to a width of each of thetows. The device may further comprise a supporting frame, and suspensionmechanisms mounting the compaction rollers on the frame for individualdisplacement relative to the frame. The compaction rollers extendsubstantially parallel to each other.

According to still a further embodiment, a method is provided ofcompacting fiber tows on a tool having at least first and second toolsurfaces respectively lying in first and second differing planesintersecting at an angle forming an edge. The method comprises moving anautomated fiber placement head over the tool surfaces, and placing fibertows on the tool surfaces with the automated fiber placement head as thefiber placement head moves over the tool surfaces. The method furthercomprises compacting the fiber tows against the tool surfaces with aplurality of compaction rollers carried on the fiber placement head,including independently adjusting the spatial orientation of thecompaction rollers as the fiber placement head traverses from the firsttool surface over the edge to the second tool surface. Compacting thefiber tows includes maintaining contact between each of the compactionrollers and least one of the fiber tows as the fiber placement headtraverses from the first surface over the edge to the second surface.The method may further comprise spring biasing each of the compactionrollers toward the tool surfaces. Moving the automated fiber placementhead includes moving the automated fiber placement head over the toolsurfaces in a direction forming an angle with the edge.

The features, functions, and advantages can be achieved independently invarious embodiments of the present disclosure or may be combined in yetother embodiments in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an illustrative embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a side elevational view of a compactiondevice on an AFP head laying fiber tows on a tool.

FIG. 2 is an illustration of an upper perspective view of the compactiondevice compacting a bandwidth of fiber tows.

FIG. 3 is an illustration of a lower perspective view of the compactiondevice.

FIG. 4 is an illustration of a top perspective view of the compactiondevice.

FIG. 5 is an illustration of a perspective view of a suspensionmechanism for mounting the compaction rollers on the supporting frame.

FIG. 6 is an illustration of an exploded, perspective view of thesuspension mechanism shown in FIG. 5.

FIG. 7 is an illustration of a diagrammatic plan view of a tool usefulin explaining how the compaction device traverses from a first toolplane at an angle over an edge to a second tool plane when laying up acourse of fiber tows having a 45° fiber orientation.

FIG. 8 is an illustration of a front elevational view of the tool,showing the relative displacement and changes in spatial orientation ofthe compaction rollers as the compaction device traverses over the edgeon the tool.

FIG. 9 is an illustration of a perspective view of the tool, showing thecompaction device traversing over the edge of the tool, and betterillustrating how the compaction rollers remain in contact with the toolsurfaces during the transition from the first tool plane to the secondtool plane.

FIG. 10 is an illustration similar to FIG. 7 but showing an elevationalview of the tool in which the compaction device has traversed from thefirst plane over the edge onto the second plane.

FIG. 11 is an illustration of a front elevational view of the tool,showing a crenulated edges of the end of a bandwidth course, and a trimline.

FIG. 12 is an illustration of a side view of a tool showing the positionof the compaction rollers when laying down fiber tows having a 90°orientation.

FIG. 13 is an illustration of a side view of a tool showing rotation ofthe compaction rollers traversing an edge on the tool when laying downfiber tows having a 0° orientation.

FIG. 14 is an illustration of a flow diagram of a method of compactingfiber tows on a tool having first and second surfaces lying in differentplanes joined along an edge.

FIG. 15 is an illustration of a flow diagram of aircraft production andservice methodology.

FIG. 16 is an illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring first to FIG. 1, an AFP head 22 is mounted on an adapter 24coupled with a robot (not shown) or similar digital numericallycontrolled manipulator for laying up composite parts on a tool 28. TheAFP head 22 includes a compaction device 20 that is adapted to compactpre-impregnated fiber tows 34 which are fed from and cut to length bythe AFP head 22. The fiber tows 34 are laid up in side-by-siderelationship, forming a conformal bandwidth 26 of the fiber tows 34. Inone embodiment, the fiber tows 34 may comprise slit prepreg tape,however principles of the disclosed embodiments are also applicable toautomated tape layup (ATL) in which full width tape is laid down andcompacted by the compaction device 20.

The embodiments are well-suited to laying up composite parts on a tool28 having undulating surfaces or surfaces lying in different planesjoined along an edge where traversing the edge with a single compactionroller may result in a portion of the roller lifting away from the toolsurface as it translates over the edge. In the illustrated example, thetool 28 includes a first, horizontal surface 29 and a second, verticalsurface 30 that intersect along a radius edge 32. As will be discussedbelow in more detail, the compaction device 20 maintains points ofcontact with the fiber tows 34 as the AFP head 22 moves from thehorizontal surface 29, over the radius edge 32 to the vertical surface30, thereby reducing or substantially eliminating non-compacted areas ofthe bandwidth 26.

Referring now to FIGS. 1-4, the compaction device 20 comprises asupporting frame 36 which, in the illustrated example, includes a pairof substantially parallel arms 38. Each of the arms 38 includes a doglegthat is secured to the AFP head 22 by suitable fasteners 50 (FIG. 1).The arms 38 are merely exemplary of a wide range of possibleconfigurations of the supporting frame 36. The compaction device 20further comprises a plurality of cylindrical compaction rollers 40 thatextend substantially parallel to each other and normally lie in a singleplane 45 (FIG. 2) when the compaction device 20 is moving over asubstantially flat tool surface, such as the horizontal tool surface 29shown in FIG. 1. Opposite ends of each of the compaction rollers 40 aremounted for displacement on the arms 38 by suspension mechanisms 35which allow the compaction rollers 40 to change their spatialorientations independently from each other.

The compaction rollers 40 may be formed of a compliant material allowingthe compaction rollers 40 to comply with minor surface irregularitieswhile applying the desired compaction force to the fiber tows 34. In oneembodiment, the pitch “P” between the central axes of adjacent ones ofthe compaction rollers 40 is substantially equal to the width “W” ofeach of the fiber tows 34, and the number of the compaction rollers 40is equal to the number of tows 34 and the bandwidth 26. The compactionrollers 40 are arranged orthogonal to the arms and each has an endjournaled for rotation in a bearing block 42, allowing the compactionroller 40 to rotate and roll over the tool 28 as it compacts thebandwidth 26 against the tool surfaces 29, 30. Each of the bearingblocks 42 is connected to one end of a cylindrical pin 46 which isslidably received in a corresponding one of the arms 38.

The suspension mechanisms 35 include springs 44 that are respectivelysleeved over the pins 46 and are captured between the bearing blocks 42and the arms 38. The force applied by the springs 44 cause the bearingblocks 42, and thus the compaction rollers 40, to be biased downwardlyagainst the tool 28. The slidable mounting of the pins 46 allow each endof the compaction rollers 40 to be independently displaced upwardly (asshown in FIG. 2) such that the spatial orientation of the compactionrollers 40 (i.e. the angular orientation of the compaction rollers) mayself-adjust based on the underlying contour and/or smoothness of thetool 28, as will be described below in more detail.

Attention is now directed to FIGS. 5 and 6 which illustrate additionaldetails of one of the suspension mechanisms 35 which mount thecompaction rollers 40 on the arms 38 in a manner that allow thecompaction rollers 42 to adjust in spatial orientation while traversingcertain features on the tool 28, such as the radius edge 32. As bestseen in FIG. 6, each of the arms 38 includes a plurality of cylindricalthrough-hole within which the cylindrical pins 46 are slidably received.The upper end of each of the pins 46 is held on the arm 38 by a snapring 52. The compaction rollers 40 are rotatably mounted on the bearingblocks 42 by axles 37 and bushings 58, 60 received within the ends ofthe compaction rollers 40. From the foregoing description, it may beappreciated that the compaction rollers 40 may move up and down relativeto the arms 38 independently of each other. Moreover, the ends of eachcompaction roller 40 may also move up and down independently of eachother, while the biasing force applied by the springs 44 maintains thedesired level of compaction on the compaction roller 40.

Attention is now directed to FIGS. 7-10 which diagrammaticallyillustrate the compaction device 20 laying down 45° fiber tows on thetool 28 shown in Figure (the AFP head 22 not shown). As the compactiondevice translates from the horizontal surface 29 onto the verticalsurface 30 and passes over the radius edge 32, the individual compactionrollers 40 pivot independently of each other such that the attitude(spatial orientation) of each compaction rollers 40 is adjusted tothereby maintain compaction force against a corresponding one of thefiber tows 34. In other words, as the AFP head rotates over the radiusedge 32, the compaction rollers 40 maintain constant point contact withthe fiber tows 34 across the entire the bandwidth 26. As a result ofthis independent adjustment of the compaction rollers 40, each of thetows 34 rolls over the radius edge 32 onto the vertical surface 30 whilea continuous compaction force is being applied to each of the tow 34 byat least one of the compaction rollers 40. The springs 44 may assist inassuring that point contact between the rollers 40 and the tows 34 ismaintained as the compaction device 20 moves over and around the radiusedge 32, and may also function to accommodate surface unevenness due,for example, to ply drop offs.

Referring to FIG. 11, due to the smaller diameter of the compactionrollers 40, compared to a single compaction roller of larger diameter,less material remains below a trim 62 at the end of each course 64.Consequently, less material is required to be trimmed away thus savingmaterial costs.

FIG. 12 shows the compaction device 20 compacting a bandwidth 26 of 0°fiber tows on the horizontal surface 29 of the tool 28. In this case,the compaction rollers 40 roll across and remain in contact thehorizontal surface 29, with no adjustment of their respective attitudes,i.e., they remain in a common plane. FIG. 13 illustrates the compactiondevice 20 compacting a bandwidth 26 of 90° fiber tows 34 on the tool 28.When compacting 90° fiber tows 34, the entire AFP head 22, and thus thecompaction device 20 rotates around the radius edge 32, onto thevertical surface 30. As the AFP head 22 rotates, the compaction rollers40 also remain in a common plane, each successively rolling over theradius edge 32.

FIG. 14 broadly illustrates the steps of a method of compacting fibertows 34 onto a tool such as a tool 28 using the compaction device 20described above. At 66, an AFP head 22 is moved over the tool 28. At 68the AFP head 22 places the fiber tows 34 on the tool 28 as the head 22moves over the tool 28. At 70, a plurality of compaction rollers 40 areused to compact the fiber tows 34 on the tool 28. The spatialorientation of the compaction rollers 40 is independently changed oradjusted as the AFP head 22 traverses from a first surface 29 on thetool 28 over an edge 32 onto a second surface 30 on the tool 28.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine, automotive applications and otherapplication where composite members such as spars and stringers areused. Thus, referring now to FIGS. 15 and 16, embodiments of thedisclosure may be used in the context of an aircraft manufacturing andservice method 72 as shown in FIG. 15 and an aircraft 74 as shown inFIG. 16. Aircraft applications of the disclosed embodiments may include,for example, without limitation, spars, stringers and other structureshaving undulations or angled corners. During pre-production, exemplarymethod 72 may include specification and design 76 of the aircraft 74 andmaterial procurement 78. During production, component and subassemblymanufacturing 80 and system integration 82 of the aircraft 74 takesplace. Thereafter, the aircraft 74 may go through certification anddelivery 84 in order to be placed in service 86. While in service by acustomer, the aircraft 74 is scheduled for routine maintenance andservice 88, which may also include modification, reconfiguration,refurbishment, and so on.

Each of the processes of method 72 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 15, the aircraft 74 produced by exemplary method 72 mayinclude an airframe 90 with a plurality of systems 92 and an interior94. Examples of high-level systems 92 include one or more of apropulsion system 96, an electrical system 98, a hydraulic system 100and an environmental system 102. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 72. For example,components or subassemblies corresponding to production process 80 maybe fabricated or manufactured in a manner similar to components orsubassemblies produced while the aircraft is in service. Also, one ormore apparatus embodiments, method embodiments, or a combination thereofmay be utilized during the production stages 80 and 82, for example, bysubstantially expediting assembly of or reducing the cost of an aircraft74. Similarly, one or more of apparatus embodiments, method embodiments,or a combination thereof may be utilized while the aircraft 74 is inservice, for example and without limitation, to maintenance and service88.

As used herein, the phrase “at least one of”, when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of each item in the list may be needed. Forexample, “at least one of item A, item B, and item C” may include,without limitation, item A, item A and item B, or item B. This examplealso may include item A, item B, and item C or item B and item C. Theitem may be a particular object, thing, or a category. In other words,at least one of means any combination items and number of items may beused from the list but not all of the items in the list are required.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different advantages as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A device for compacting a bandwidth of fiber towson a tool, comprising: a frame adapted to be moved over surfaces of thetool; and a plurality of compaction rollers mounted on the frame forindependent relative displacement, each of the compaction rollersadapted to compact the tows onto the surfaces of the tool.
 2. The deviceof claim 1, wherein: the frame includes a pair of spaced apart arms, andthe compaction rollers extend between and have opposite ends thereofrespectively rotatably mounted on the pair of arms.
 3. The device ofclaim 1, wherein each of the compaction rollers has first and secondopposite ends, and the device further comprises: pins fixed to each ofthe first and second ends of the compaction rollers and slidely mountingthe compaction roller on the frame.
 4. The device of claim 3, furthercomprising: a spring on each of the first and second opposite ends ofthe compaction rollers for biasing the compaction rollers toward thesurfaces of the tool.
 5. The device of claim 1, wherein the compactionrollers extend substantially parallel to each other.
 6. The device ofclaim 5, wherein: the tows each have a width, there is a pitch betweencenters of the compaction rollers, and the pitch is substantially equalto the width of the tows.
 7. The device of claim 1, wherein: thecompaction rollers normally lie in a single plane, and at least certainof the compaction rollers are adapted to move out of the single planewhen the compaction rollers traverse over an edge of the surfaces of thetool.
 8. The device of claim 1, further comprising: a bearing block ateach end of each of the compaction rollers, wherein each end of thecompaction rollers is journaled for rotation in one of the bearingblocks; pins respectively fixed to the bearing blocks and slidablymounted on the frame; and springs respectively sleeved over the pins forbiasing the bearing blocks toward the surfaces of the tool.
 9. Thedevice of claim 1, wherein the compaction rollers are equal in number tothe fiber tows.
 10. A device for compacting a bandwidth of fiber tows ona tool having tool surfaces intersecting at an angle forming an edge onthe tool, comprising: a pair of arms spaced apart from each other; and aplurality of displaceable compaction rollers extending between the armsand mounted on the arms for independent displacement relative to eachother as the compaction rollers traverse over the edge of the tool. 11.The device of claim 10, wherein each of the compaction rollers is springbiased toward the tool surfaces.
 12. The device of claim 10, wherein thecompaction rollers extend substantially parallel to each other andnormally lie in a single plane but are individually displaceable out ofthe single plane when traversing the edge on the tool.
 13. The device ofclaim 10, wherein compaction rollers are substantially equal in numberto the fiber tows in the bandwidth.
 14. The device of claim 10, whereina distance between centers of adjacent ones of the compaction rollers issubstantially equal to a width of each of the tows.
 15. The device ofclaim 10, further comprising: a supporting frame; and suspensionmechanisms mounting the compaction rollers on the frame for individualdisplacement relative to the frame.
 16. The device of claim 10, whereinthe compaction rollers extend substantially parallel to each other. 17.A method of compacting fiber tows on a tool having at least first andsecond tool surfaces respectively lying in first and second differingplanes intersecting at an angle to form an edge, comprising: moving anautomated fiber placement head over the tool surfaces; placing fibertows on the tool surfaces with the automated fiber placement head as thefiber placement head moves over the tool surfaces; and compacting thefiber tows against the tool surfaces with a plurality of compactionrollers carried on the automated fiber placement head, includingindependently adjusting a spatial orientation of the compaction rollersas the automated fiber placement head traverses from the first toolsurface over the edge to the second tool surface.
 18. The method ofclaim 17, wherein compacting fiber tows includes maintaining contactbetween each of the compaction rollers and least one of the fiber towsas the automated fiber placement head traverses from the first surfaceover the edge to the second surface.
 19. The method of claim 17, furthercomprising: spring biasing each of the compaction rollers toward thetool surfaces.
 20. The method of claim 17, wherein moving the automatedfiber placement head includes moving the automated fiber placement headover the tool surfaces in a direction forming an angle with the edge.